1. Field of the Invention
The present invention relates to a balanced-output triplexer which separates three signals of different frequency bands inputted to an input terminal, and outputs them as balanced signals from respective corresponding balanced output terminals.
2. Description of the Related Art
In recent years, miniaturization has been demanded of wireless communication apparatuses such as a wireless LAN (local area network) communication apparatus, a WiMAX™ (Worldwide Interoperability for Microwave Access) communication apparatus, and a cellular phone. Meanwhile, capability to process a plurality of reception signals of different frequency bands in a single apparatus has been required as well.
In order for a single wireless communication apparatus to process a plurality of reception signals of different frequency bands, it is necessary to implement means for separating the plurality of reception signals received by an antenna from each other. Among known means for separating three reception signals of different frequency bands are triplexers such as those described in JP-A-2003-198309, JP-A-2006-108824, JP-A-2006-211057, and JP-A-2006-333258. The conventional triplexers have been configured to output the three separated reception signals each in the form of an unbalanced signal.
When implemented in a wireless communication apparatus, a triplexer is connected to signal processing circuitry for performing amplification, demodulation and other processing on the three reception signals. Lately, this signal processing circuitry has often been configured as an integrated circuit. The integrated circuit is often designed to accept signals each in the form of a balanced signal. If a triplexer that outputs three reception signals each in the form of an unbalanced signal and an integrated circuit that accepts reception signals each in the form of a balanced signal are to be employed in a wireless communication apparatus, then it is necessary to provide baluns for converting unbalanced signals into balanced signals between the respective reception signal output terminals of the triplexer and the respective reception signal input terminals of the integrated circuit. However, this hampers the miniaturization of the wireless communication apparatus and makes it difficult to connect the respective reception signal output terminals of the triplexer to the respective reception signal input terminals of the integrated circuit.